title: Factors affecting photopolymerization stress in dental composites.
abstract: Polymerization stress development results from the complex interplay of volumetric shrinkage, reaction kinetics, and viscoelastic properties. The objective of this study was to examine the relationships among volumetric shrinkage, degree of conversion, rate of polymerization (RP(max)), and stress development for 2 model bis-GMA-based composites. Three irradiances were used--220, 400, or 600 mW/cm(2)--with exposure times adjusted to deliver the same radiant energy. Volumetric shrinkage was determined with a mercury dilatometer, degree of conversion and RP(max) by differential scanning calorimetry (DSC), and polymerization stress with a low-compliance device (Sakaguchi et al., 2004b). Results indicated that polymerization reaction rate and shrinkage were not correlated. Irradiance was directly related to polymerization reaction rate and to stress development. The group with the highest stress/degree of conversion exhibited the lowest RP(max), so it can be assumed, within the limitations of this study, that the conversion was most closely related to stress development.
authors.affiliation: Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227 São Paulo, SP, Brazil. pfeifercs@gmail.com
authors.forename: C S
authors.initials: CS
authors.lastname: Pfeifer
authors.forename: J L
authors.initials: JL
authors.lastname: Ferracane
authors.forename: R L
authors.initials: RL
authors.lastname: Sakaguchi
authors.forename: R R
authors.initials: RR
authors.lastname: Braga
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects*; D002152:Calorimetry, Differential Scanning; D003799:Dental Stress Analysis; D006244:Hardness; D007700:Kinetics; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates / Q000528:radiation effects; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000528:radiation effects; D011140:Polyurethanes / Q000528:radiation effects
chemical_list: D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate